Go语言系列（七）- 读写操作

package main

import (
	"fmt"
)

var (
	firstName, lastName, s string
	i                      int
	f                      float32
	input                  = "56.12 / 5212 / Go"
	format                = "%f / %d / %s"
)

func main() {
	fmt.Println("Please enter your full name: ")
	fmt.Scanln(&firstName, &lastName)
	// fmt.Scanf("%s %s", &firstName, &lastName)
	fmt.Printf("Hi %s %s!\n", firstName, lastName) // Hi Chris Naegels
	fmt.Sscanf(input, format, &f, &i, &s)
	fmt.Println("From the string we read: ", f, i, s)
}

package main

import (
	"bufio"
	"fmt"
	"os"
)

var inputReader *bufio.Reader
var input string
var err error

func main() {
	inputReader = bufio.NewReader(os.Stdin)
	fmt.Println("Please enter some input: ")
	input, err = inputReader.ReadString(‘\n‘)
	if err == nil {
		fmt.Printf("The input was: %s\n", input)
	}
}

package main

import (
	"bufio"
	"fmt"
	"os"
)

func file_write() {
	// 文件读写
	file, err := os.OpenFile("test.log", os.O_CREATE|os.O_WRONLY, 0664)
	if err != nil {
		fmt.Println("open file err,:", err)
		return
	}
	fmt.Fprintf(file, "do balance error\n")
	file.Close()
}

func main() {
	// file_write()
	file, err := os.Open("test.log")
	if err != nil {
		fmt.Println("read file failed, err：", err)
		return
	}

	defer file.Close()

	reader := bufio.NewReader(file)
	str, err := reader.ReadString(‘\n‘)
	if err != nil {
		fmt.Println("read string failed, err：", err)
		return
	}

	fmt.Printf("read str success, ret: %s\n", str)
}

package main

import (
	"fmt"
	"io/ioutil"
	"os"
)

func main() {

	inputFile := "products.txt"
	outputFile := "products_copy.txt"
	buf, err := ioutil.ReadFile(inputFile)
	if err != nil {
		fmt.Fprintf(os.Stderr, "File Error: %s\n", err)
		return
	}

	fmt.Printf("%s\n", string(buf))
	err = ioutil.WriteFile(outputFile, buf, 0x644)
	if err != nil {
		panic(err.Error())
	}
}

package main

import (
	"bufio"
	"compress/gzip"
	"fmt"
	"os"
)
func main() {
	fName := "MyFile.gz"
	var r *bufio.Reader
	fi, err := os.Open(fName)
	if err != nil {
		fmt.Fprintf(os.Stderr, "%v, Can’t open %s: error: %s\n", os.Args[0], fName, err)
		os.Exit(1)
	}
	fz, err := gzip.NewReader(fi)
	if err != nil {
		fmt.Fprintf(os.Stderr, "open gzip failed, err: %v\n", err)
		return
	}
	r = bufio.NewReader(fz)
	for {
		line, err := r.ReadString(‘\n‘)
		if err != nil {
			fmt.Println("Done reading file")
			os.Exit(0)
		}
		fmt.Println(line)
	}
}

os.OpenFile(“output.dat”, os.O_WRONLY|os.O_CREATE, 0666)

package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	outputFile, outputError := os.OpenFile("output.dat", 
os.O_WRONLY|os.O_CREATE, 0666)
	if outputError != nil {
		fmt.Printf("An error occurred with file creation\n")
		return
	}

	defer outputFile.Close()
	outputWriter := bufio.NewWriter(outputFile)
	outputString := "hello world!\n"
	for i := 0; i < 10; i++ {
		outputWriter.WriteString(outputString)
	}
	outputWriter.Flush()
}

package main

import (
	"fmt"
	"io"
	"os"
)

func main() {

	CopyFile("target.txt", "source.txt")
	fmt.Println("Copy done!")
}

func CopyFile(dstName, srcName string) (written int64, err error) {
	src, err := os.Open(srcName)
	if err != nil {
		return
	}
	defer src.Close()
	dst, err := os.OpenFile(dstName, os.O_WRONLY|os.O_CREATE, 0644)
	if err != nil {
		return
	}
	defer dst.Close()
	return io.Copy(dst, src)
}

package main

import (
	"bufio"
	"fmt"
	"io"
	"os"
)

type CharCount struct {
	ChCount    int
	NumCount   int
	SpaceCount int
	OtherCount int
}

func main() {
	file, err := os.Open("test.log")
	if err != nil {
		fmt.Println("read file failed, err：", err)
		return
	}

	defer file.Close()

	var count CharCount

	reader := bufio.NewReader(file)
	for {
		str, err := reader.ReadString(‘\n‘)
		if err == io.EOF {
			break
		}
		if err != nil {
			fmt.Printf("read file failed, err%s", err)
			break
		}
		runeArr := []rune(str)
		for _, v := range runeArr {
			switch {
			case v >= ‘a‘ && v <= ‘z‘:
				fallthrough
			case v >= ‘A‘ && v <= ‘Z‘:
				count.ChCount++
			case v == ‘ ‘ || v == ‘\t‘:
				count.SpaceCount++
			case v >= ‘0‘ && v <= ‘9‘:
				count.NumCount++
			default:
				count.OtherCount++
			}
		}
	}
	fmt.Printf("char count: %d\n", count.ChCount)
	fmt.Printf("num count: %d\n", count.NumCount)
	fmt.Printf("space count: %d\n", count.SpaceCount)
	fmt.Printf("other count: %d\n", count.OtherCount)
}

package main

import (
	"bufio"
	"flag"
	"fmt"
	"io"
	"os"
)

func cat(r *bufio.Reader) {
	for {
		buf, err := r.ReadBytes(‘\n‘)
		if err == io.EOF {
			break
		}
		fmt.Fprintf(os.Stdout, "%s", buf)

		return
	}
}

func main() {
	flag.Parse()
	if flag.NArg() == 0 {
		cat(bufio.NewReader(os.Stdin))
	}
	for i := 0; i < flag.NArg(); i++ {
		f, err := os.Open(flag.Arg(i))
		if err != nil {
			fmt.Fprintf(os.Stderr, "%s:error reading from %s: %s\n",
				os.Args[0], flag.Arg(i), err.Error())
		}
		continue
	}
	cat(bufio.NewReader(f))
}

package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	fmt.Fprintf(os.Stdout, "%s\n", "hello world! - unbuffered")
	buf := bufio.NewWriter(os.Stdout)
	fmt.Fprintf(buf, "%s\n", "hello world! - buffered")
	buf.Flush()
}

package main

import (
	"flag" // command line option parser
	"fmt"
)

func main() {

	var test bool
	var str string
	var count int
	flag.BoolVar(&test, "b", false, "print on newline")
	flag.StringVar(&str, "s", "", "print on newline")
	flag.IntVar(&count, "c", 1001, "print on newline")
	flag.Parse()

	fmt.Println(test)
	fmt.Println(str)
	fmt.Println(count)
}

package main

import (
	"encoding/json"
	"fmt"
)

type User struct {
	UserName string `json:"username"`
	Nickname string `json:"nickname"`
	Age      int
	Birthday string
	Sex      string
	Email    string
	Phone    string
}

func testStruct() {
	user1 := &User{
		UserName: "user1",
		Nickname: "超级英雄",
		Age:      18,
		Birthday: "2008/8/8",
		Sex:      "男",
		Email:    "mayun@qq.com",
		Phone:    "110",
	}
	data, err := json.Marshal(user1)
	if err != nil {
		fmt.Println("json.marsha1 failed, err:", err)
		return
	}
	fmt.Printf("%s\n", string(data))
}

func testInt() {
	var age = 100
	data, err := json.Marshal(age)
	if err != nil {
		fmt.Println("json.marsha1 failed, err:", err)
		return
	}
	fmt.Printf("%s\n", string(data))
}

func testMap() {
	var m map[string]interface{}
	m = make(map[string]interface{})
	m["username"] = "user1"
	m["age"] = 18
	m["sex"] = "女"
	data, err := json.Marshal(m)
	if err != nil {
		fmt.Println("json.marsha1 failed, err:", err)
		return
	}
	fmt.Printf("%s\n", string(data))
}
func testSlice() {
	var m map[string]interface{}
	var s []map[string]interface{}
	m = make(map[string]interface{})
	m["username"] = "user1"
	m["age"] = 18
	m["sex"] = "女"

	s = append(s, m)

	data, err := json.Marshal(s)
	if err != nil {
		fmt.Println("json.marsha1 failed, err:", err)
		return
	}
	fmt.Printf("%s\n", string(data))
}
func main() {
	testStruct()
	testInt()
	testMap()
	testSlice()
}　　

package main

import (
	"errors"
	"fmt"
)

var errNotFound error = errors.New("Not found error")

func main() {
	fmt.Printf("error: %v", errNotFound)
}

type error interface { 
        Error() string 
} 

package main
import (
//	"fmt"
)
type PathError struct {
	Op   string
	Path string
	err string
}
func (e *PathError) Error() string {
	return e.Op + " " + e.Path + ": " + e.Err.Error()
}
func test() error {
	return &PathError{
		Op:   "op",
		Path: "path",
	}
}
func main() {
	test()
}

switch err := err.(type) {
case ParseError:
         PrintParseError(err)
case PathError:
         PrintPathError(err)
... default: 
} 

package main

import (
	"fmt"
)

func badCall() {
	panic("bad end")
}

func test() {
	defer func() {
		if e := recover(); e != nil {
			fmt.Printf("Panicking %s\r\n", e)
		}
	}()
	badCall()
	fmt.Printf("After bad call\r\n")
}

func main() {
	fmt.Printf("Calling test\r\n")
	test()
	fmt.Printf("Test completed\r\n")
}